A prospective cohort study about the incidence of nosocomial infection (NI) was carried out on 671 patients treated at Pediatric Intensive Care Unit in 14 months. The incidence of NI was 22.9% and 29.3/1000 patient-days, in which nosocomial pneumonia accounts for 49.4%, 43.1/1000 ventilator-days; septicema: 27.3%, 49.3/1000 central catheter-days; surgical site infection: 12.3%, catheter-induced infection: 11.7%; urinary tract infection: 58%, 41.9/1000 urinary catheter-day. Day of onset NI was 6.4±5 days. NI rate is higher in moderate malnutrition, co-morbidities, immunocompromise patients. Main causes were gram negative (79.8%). The mortality rate of the patients with NI was 36.4% significantly higher than that of the patients without NI (8.6%)